Therapeutic Agent for Neuropathic Pain

Abstract

The present invention provides therapeutic agents for neuropathic pain, the agents having excellent therapeutic effects on neuropathic pain, which is an intractable disorder. More specifically, the invention provides therapeutic agents for neuropathic pain comprising, as the active ingredient, an opioid receptor antagonist (particularly naloxone, naltrexone, naloxonazine, naltrindole, etc.), pharmaceutical compositions for treating neuropathic pain comprising an opioid receptor antagonist as the active ingredient, and a method for treating neuropathic pain using opioid receptor antagonists.

1 . A therapeutic agent for neuropathic pain adapted for administering, as an active ingredient, an opioid receptor antagonist in a dose of between 100 and 25,000 mg per day.  
     
     
         2 . The therapeutic agent for neuropathic pain of  claim 1 , wherein the opioid receptor antagonist is a subtype-nonselective opioid receptor antagonist.  
     
     
         3 . The therapeutic agent for neuropathic pain of  claim 2 , wherein the subtype-nonselective opioid receptor antagonist is selected from the group consisting of naloxone, naltrexone, diprenorphine, β-chlornaltrexamine, nalmefene, (9-[3-(cis-2,5-dimethyl-1-piperazinyl)propyl]carbazole dihydrochloride and pharmaceutically acceptable salts thereof.  
     
     
         4 . The therapeutic agent for neuropathic pain of  claim 3 , wherein the subtype nonselective opioid receptor antagonist is selected from the group consisting of naloxone, naltrexone and pharmaceutically acceptable salts thereof.  
     
     
         5 . The therapeutic agent for neuropathic pain of  claim 1 , wherein the opioid receptor antagonist is a subtype-selective opioid receptor antagonist.  
     
     
         6 . The therapeutic agent for neuropathic pain of  claim 5 , wherein the subtype-selective receptor antagonist is a μ subtype-selective opioid receptor antagonist.  
     
     
         7 . The therapeutic agent for neuropathic pain of  claim 6 , wherein the μ subtype-selective opioid receptor antagonist is selected from the group consisting of naloxonazine, CTAP, CTOP, β-funaltrexamine, methocinnamox, cyprodime, 3-methoxynaltrexone and pharmaceutically acceptable salts thereof.  
     
     
         8 . The therapeutic agent for neuropathic pain of  claim 7 , wherein the μ subtype-selective opioid receptor antagonist is selected from naloxonazine and pharmaceutically acceptable salts thereof.  
     
     
         9 . The therapeutic agent for neuropathic pain of  claim 5 , wherein the subtype-selective receptor antagonist is a δ subtype-selective opioid receptor antagonist.  
     
     
         10 . The therapeutic agent for neuropathic pain of  claim 9 , wherein the δ subtype-selective opioid receptor antagonist is selected from the group consisting of naltriben, naltrindole, BNTX, DALCE, 5′-NTII, NTB, TIPP (Ψ), ICI-174,864 and pharmaceutically acceptable salts thereof.  
     
     
         11 . The therapeutic agent for neuropathic pain of  claim 10 , wherein the δ subtype-selective opioid receptor antagonist is selected from naltrindole and pharmaceutically acceptable salts thereof.  
     
     
         12 . The therapeutic agent for neuropathic pain of  claim 1 , wherein the neuropathic pain is one or more symptoms selected from the group consisting of postherpetic neuralgia, trigeminal neuralgia, diabetic neuralgia, cancer pain, persistent postoperative or posttraumatic pain, hyperalgia, allodynia, postthoracotomy pain, CRPS, pain associated with multiple sclerosis, AIDS, thalamic pain, paraplegic pain caused by myelopathy, anesthesia dolorosa and phantom limb pain.  
     
     
         13 . A drug composition for treating neuropathic pain, comprising an opioid receptor antagonist in a dose of between 100 and 25,000 mg per day and a pharmaceutically acceptable carrier.  
     
     
         14 . A method for treating neuropathic pain, comprising administering an opioid receptor antagonist to a mammal in a dose of between 100 and 25,000 mg per day.  
     
     
         15 . (canceled)